Safety brake tripping system for elevators



Filed May 6, 1966 R. F. MARTIN SAFETY BRAKE TRI'PPING SYSTEM FORELEVATORS 5 Sheets-Sheet 1 F I6. IA

INVENTOR v RICHARD E MART/N Oct. 10, 1967 R. F. MARTIN 3,346,073

SAFETY BRAKE TRIPPING SYSTEM FOR ELEVATORS Filed May 6, 1966 5Sheets-Sheet 2 Q'qu'u A A j, 32 32 "1'' El 37 7 30 30 J I 3/ F 6. 2 3/ l22 0a. 10, 1967 R, F, MARTW 3,346,073

SAFETY BRAKE TRIPPING SYSTEM FOR ELEVATORS Filed May 6, 1966 5Sheets-Sheet 5 /3 r W W 53 Oct. 10, 1967- R. F. MARTIN 3,346,073

SAFETY BRAKE TRIPI ING SYSTEM FOR ELEVATORS Filed May 6, 1966 5Sheets-Sheet 4 Oct. 10, 1967 MART|N 3,346,073

SAFETY BRAKE TRIPPING SYSTEM FOR ELEVATORS Filed May 6, 1966 5Sheets-Sheet 5 #fiv Fl 6. M

United States Patent Office 3,346,073 SAFETY BRAKE TRTPPING SYSTEM FORELEVATORS Richard F. Martin, Rock Island, 111., assignor to MontgomcryElevator Company, a corporation of Delaware Filed May 6, 1966, Ser. No.548,222 6 Claims. (Cl. 187-90) ABSTRACT OF THE DISCLOSURE Trippingmechanism for an elevator safety brake, in which a shaft that rotates ata speed directly proportional to the speed of the elevator is providedwith acceleron1 eter means which trips the safety brake if the rate ofac celeration of rotation of the shaft exceeds a predetermined maximumvalue.

Elevator systems always include an over speed control which has atripping device to set car brakes on the elevator car guide rails in theevent of motor failure or a breakage in the hoisting cables for the car.The over speed control is a safety device which is divorced from thehoisting motor and cable apparatus to set the car brakes on the guiderails independently of the operating controls for the elevator.

It is old in the art to employ flyballs which, in the event of excessivespeed of the elevator car, operate on the basis of centrifugal force tomove a shaft that operates through levers to shut down the elevatormotor and set the brakes on the elevator guide rails. Such speedcontrolled flyball tripping devices include massive balls or discsconnected to a rotating shaft by pivoted link arms. The shaft rotates indirect proportion to the speed of descent of the elevator car.

The tripping device must, of course, be set to trip the brake at a speedhigher than the fastest possible down travel of the car in normaloperation. On cars which operate at a maximum speed of 300 to 400 f.p.m.the conventional flyball actuated device is adequate; but it has beendiscovered that in higher speed elevators, which may travel at 500 to800 f.p.m., conditions develop in flyball units that cause them to lagand trip at a dangerously high speed. Instead of tripping the brake, forexample, at 950 f.p.m. on a car designed for 800' f.p.m. the flyball maynot trip the brake until the car reaches 1300 to 1500 f.p.m.; and this,of course, creates a dangerous situation that far exceeds state safetyspecifications. To the best of my knowledge, the reason for thisbehavior of flyball devices has not heretofore been known.

The flyballs are on a shaft which rotates constantly when the elevatoris in motion, and if an elevators normal operating speed is 800 f.p.m.,the rotational speed of the flyballs is quite high. I have nowdiscovered that at speeds of rotation produced by an elevator speed inexcess of about 500 f.p.m., the flyballs tend to lag behind a radialdisposition with respect to the shaft on which they are mounted, andthis flexes the flyball links enough to cause binding in the linkpivots. The result is a frictional drag which requires highercentrifugal force to move the flyballs than should theoretically berequired, so the elevator speed necessary to move the flyballs out fromthe shaft is far greater than would be expected. The effect, of course,tends to be cumulative if a malfunction causes the elevator car toapproach a free fall condition. Thus the car reaches an unsafe speedbefore the balls are able to move enough to trip the brake mechanism.

The device of the present invention is designed for use either as anaccessory added to the rotating shaft of a flyball device, or as a newand improved safety brake Bfitfifilli Patented Oct. 10, 1967 trippingsystem for newly installed elevators. Briefly, the

. shaft of the tripping assembly and the other of which is an inertiamember of relatively large mass journalled on the shaft so that uponacceleration of the shaft the inertia member may lag behind the fixedmember. The resulting relative movement between the two members tripsthe safety brake on the elevator car.

The principal object of this invention, therefore, is to provide anelevator safety brake tripping device which is operated by excessiveacceleration of the elevator car rather than by excessive speed.

Another object is to provide a tripping device which sets the brakes ona high speed elevator before it can reach a dangerous rate of descent.

Still a further object of this invention is to provide a safety brakesystem of the character described which includes means for adjusting therate of acceleration at which relative movement of the relativelymovable members occurs.

Other objects and advantages of the invention will become readilyapparent from the following detailed description taken in connectionwith the accompanying drawings,

in which:

FIG. 1 is a schematic view of an elevator safety brake system with aflyball tripping device to which the device of the present invention isadded as an accessory;

FIG. 1A is a schematic view of the bottom of the elevator car;

FIG. 2 is an elevational view of the flyball type tripping device ofFIG. 1 with portions cut away for clarity;

FIG. 3 is a side elevational view of the flyball tripping device, andshows the structure of the present invention which is added thereto;

FIG. 4 is a fragmentary sectional view of the struc ture of thisinvention;

FIG. 5 is an elevational view with parts broken away, taken generallyalong the line 55 of FIG. 4;

FIG. 6 is an elevational view of the safety brake means mounted on thebottom supporting cross beam of an elevator car; and

FIG. 7 is a bottom plan view of the safety brake means of FIG. 6.

As illustrated in FIG. 1, an elevator system is shown to comprise anelevator car 10 movable on T-s haped guide rails 11 which are verticallymounted on the side walls of the elevator shaft. The elevator car movesup and down within the elevator shaft in response to a master control,generally comprising an elevator motor and a hoisting cable (none ofwhich is illustrated in the drawings). A standard flyball brake trippingdevice, generally designated 12, is mounted above the elevator shaft inthe machinery penthouse of the elevator system. Such a device is an overspeed control which sets brakes on the guide rails 11 in response toexcessively rapid downward travel of an elevator car resulting, forexample, from failure of the elevator motor or breakage of the hoistingcable. The tripping device 12 has a control sheave l3; and a cable 14passes around said sheave, around a tail sheave 15 in the pit, and has aconnector, generally designated 16, fixed to the elevator cross head 17so that the control sheave 13 and its shaft (hereinafter described)rotate at a speed which is directly proportional to the speed of descentof the elevator car. The tripping device 12 and c.ble 14 are divorcedfrom main cable and operating controls of the elevator.

Referring now'to FIGS. 2 and 3 which illustrate the flyball trippingdevice in detail, a frame 18 supports a pillow block 19 for a shaft 20on which the control sheave '13 is fixed; and surmounting the frame 18is a bearing bracket 21 in which a vertical sleeve 22 is journalled. Abeveled ring gear 23 on the sheave 13 meshes with a beveled pinion gear24 on the sleeve, so that the latter is driven by the cable 14 throughthe sheave 13.

A vertical shaft 25 is journalled and slidably mounted in the sleeve 22and in a bushing 26 on the frame 18, and a fiyball assembly, indicatedgenerally at 27, is linked to the sleeve 22 through a head 28 and to theshaft 25 through a bracket 29. The fiyball assembly includes lower links30 which are pivoted at 31 to the head 28, massive flyball discs 32which are pivoted to the links 30 at 33, and upper links 34 which extendfrom the pivots 33 and are pivoted at 35 to the bracket 29. The upperend of the shaft 25 is threaded to receive nuts 36 which provideadjustable stops for a compression spring 37 that biases the shaft 25upwardly.

Journalled at the lower end of shaft 25 is a yoke 38, and a push rod 39is pinned to the yoke at 40 so that vertical movement of the shaft movesthe push rod 39 up and down.

The flyballs 32 rotate with the sleeve 22 and shaft 25, and centrifugalforce tends to fling them radially outwardly to lower the links 30 and34 and move the shaft 25 and push rod 39 down against the bias of thespring 37; and said spring is adjusted so that the flyballs may moveoutwardly only when the sleeve 22 rotates fast enough for centrifugalforce to overcome the spring bias.

The brake tripping mechanism also includes operating linkage means,indicated generally at 41, for moving a brake shOe 42 which clamps thecable 14 against a brake anvil 43. The linkage means 41 includes a lever44 pivoted on the upper end of an arm 45 at point 46. The arm 45 ispivoted at its lower end to the frame 18 at point 47. A compressionspring mechanism 48 which is secured to the arm 45 limits the clampingforce on the brake shoe 42 by permitting the arm to rockcounterclockwise when clamping thrust on the lever 44 exceeds the forcerequired to compress the spring. An adjustable stop 49 limits upwardmovement of the lever 41. A stud 50 on the lever 44 impales a slot 51 inthe push rod 39, so downward movement of the shaft 25, in response tothe centrifugal force acting on the flyballs 32, acts through push rod39 to urge the lever 44 about pivot 46 in the direction of arrow C andforce brake shoe 42 in the direction of arrow D and clamp cable 14. Aswill be more fully described below, the clamping of cable 14 trips asafety brake mounted on the bottom of the elevator car to clamp theguide rails 11 in the elevator shaft to stop the descent of the elevatorcar.

It should be noted that the downward movement of shaft 25 also actsthrough a switch link 52 leading to a known switching mechanism,generally designated 52a, to shut down the elevator motor. The entirestructure as described to this point is old mechanism.

As best illustrated in FIG. 3, the accelerometer device of the presentinvention, indicated generally at 53, may be used as an accessory to bemounted on the shaft 20 of the control sheave 13 of a standard flyballgovernor. Of course, the device is equally adaptable as an improvedsafety brake system for newly installed elevators. Referring to FIG. 4,the device operates on the basis of an accelerometer means which iscomprised of a plurality of relatively movable members which moverelative to one another only when the maximum permissible rate ofacceleration of the elevator car is exceeded. It includes a firstsrotating plate member 54 fixed to the shaft 20 and an inertia member 55journalled on the shaft 20 as by ball bearings 56. The inertia member 55is of a relatively large 4 mass so that upon acceleration of the shaft20 the inertia member tends to lag behind the first plate 54 to afiordrelative movement between the first plate and the inertia member.

Referring to FIG. 5, a tension spring 57 is connected at one end to abracket 58 which extends outwardly from the first plate 54 and isconnected at its other end to a lug 59 which extends inwardly from theinertia member 55 through a slot 60 in the first plate 54. The spring 57predetermines the maximum rate of acceleration permissible for theelevator car. At all rates of acceleration below said maximum rate, thespring 57 connected to the first plate 54 drags the inertia member 55along for simultaneous rotation with the plate 54. The slot 60 in thefirst plate 54 is elongated so the lug 59 may move in the direction ofarrow E (FIG. 5) when the maximum permissible rate of acceleration isexceeded and the inertia member 55 lags behind the first plate 54. Itshould be noted that the spring 57 is threadedly connected to thebracket 58 and lug 59 to permit its tension to be changed and thusadjust the rate of acceleration at which the inertia members lag behindthe first plate 54.

The device includes a second plate member 61 mounted on the shaft 20 forrotational movement therewith and for rectilinear sliding movementrelative to the first plate 54. A spring 62 urges the second plate 61away from the first plate 54. A latch means is fixedly mounted on thelug 59 of the inertia member 55 and includes a finger 63 extendingthrough an aligned release recess 64 (FIG. 5) in the second plate 61 torestrain the latter against movement under the urging of spring 62. Alatch lug 65 on finger 64 bears against the inner face 66 of the secondplate 61. When the maximum rate of acceleration is achieved, rotation ofthe first plate 54 relative to the inertia member 55 causes the latchlug 65 to move into the release recess 64 in the second plate member 61.The second plate 61 then snaps to the left (in FIG. 4) under the forceof spring 62. A bell crank 67 is pivoted on frame 18 and has a first leg68 with a follower roller 69 which bears against the inner face 66 ofthe second plate 61. A second leg 70 of the bell crank 67 makes a pinand slot connection 71 with the upper end of a brake shoe trip rod 72,which is guided in an eye 73 on the frame 18. As the plate 61 slides tothe left in FIG. 4, the bell crank is moved about pivot 74, asillustrated in an exaggerated phantom position in FIG. 4, causing thesecond leg 70 of the bell crank to move the trip rod 72 downwardly.Thus, the plate 61 serves as actuating means for the brake trippingmeans. Referring to FIGS. 2 and 5, as the trip rod 72 moves downwardlyit moves lever 44 to force brake shoe 42 into clamping relationship withcable 14 as above described.

In operation, the inertia member 55, the first plate 54, and therectilinearly movable second plate 61 rotate together with shaft 20 atall rates of acceleration below the rate at which spring 57 stretches.At these normal rates of acceleration, the inertia member 55 is draggedalong with first plate 54. If a sudden rate of acceleration beyond thepermissible limit of the tension in spring 57 is caused bymalfunctioning of the elevators main controls, for instance, the firstplate 54 will run away from the inertia member 55 because of therelatively large mass of the latter. The latch lug 65 will then moveinto the release recess 64 in the second plate 61 thereby permittingspring 62 to rectilinearly move the second plate 61 against the camfollower 69 of bell crank 67, thus pivoting the bell crank about point74 to cause the brake shoe trip rod 72 to move downwardly against lever44 connected to the brake shoe 42, as above described.

FIGS. 1, 6 and 7 disclose the safety brake which is set in response tothe clamping of cable 14, The connector 16 (FIG. 1) connecting cable 14to the cross head 17 of the elevator car includes a well knownreleasable jaw to releasably secure cable 14 to the elevator cross head.A brake actuating cable 75 is secured to connector 16 at one end andextends the height of the car and is wrapped around a first verticallyoriented pulley P1 on the bottom of the elevator car (FIG. 1A). Thecable 75 then wraps a second horizontally oriented pulley P2 and leadsto a cable drum 76 (FIGS. 5 and 6) on the bottom of the elevator car.Thus, when cable 14 is clamped by the accelerometer controlled braketripping device, the descent of the elevator car releases the jaw meansof the cable connector 16 and the upper end of brake actuating cable 75which is secured to cable 16. As the car continues its descent, thecable 75 unwinds from the brake drum 76, causing the drum to rotate andset the safety brake on the elevator car.

Referring particularly to FIGS. 6 and 7, shafts 77 and 78 extendlaterally on the underside of the elevator car from either side of thecable drum 76 and are arranged to rotate in opposite directions as thecable drum rotates. The shafts are threaded into jaw means, generallydesignated 79, so that rotation of the shafts 77 and 78 causes theopposing jaws 80a and 80b (FIG. 7) to move in the direction of arrows Fabout pivot 81 and thus clamp the leg portions 11a of the T-shaped guiderails 11 to Stop the elevator car.

Thus it can be seen that I have provided a new and improved safety brakedevice which operates on the principle of an accelerometer to stop thefall of a malfunctioning elevator car before the car could reach thetripping speed of an ordinary fiyball device. The unit is easilyadjustable to various predetermined rates of maximum acceleration. It issimple and easily constructed, and may be employed either as anaccessory for presently operated fiyball type brake trips and the likeor as a new safety brake tripping device without flyballs.

I claim:

1. In a safety brake system for elevator cars, brake tripping meanscomprising, in combination: a frame; a shaft journalled on said frame;means for rotating said shaft at a speed which is directly proportionalto the speed of descent of the elevator car; accelerometer means on saidshaft for detecting a rate of acceleration of said shaft in excess of apredetermined maximum rate, said accelerometer means having a pluralityof relatively movable members which move relative to one another onlyWhen said maximum rate of acceleration is exceeded; and means carried onthe shaft and movable relative to the shaft, said last named means beingactivated by relative movement of said members for tripping a safetybrake on said elevator car.

2. The brake tripping means of claim 1 in which the 6 accelerometermeans includes means for adjusting the rate of acceleration at whichrelative movement of the relatively movable members occurs.

3. The brake tripping means of claim 1 in which the accelerometer meansincludes a first member which is fixed on the shaft, an inertia memberjournalled on said shaft, said inertia member being of relatively largemass so that upon acceleration of the shaft the inertia member may lagbehind the first member to afford relative movement between the firstmember and the inertia member, and resilient means connecting the firstmember and the inertia member for simultaneous rotation and accelerationat all rates of acceleration below said maximum rate.

4. The brake tripping means of claim 3 which includes means foradjusting the tension on the resilient connecting means so as to adjustthe rate of acceleration at which the inertia member may lag behind thefirst member.

5. The brake tripping means of claim 3 which includes a second membermounted on the shaft for rectilinear sliding movement relative to thefirst member, spri means urging the second member away from the firstmember, latch means engaging the second member to restrain the latteragainst movement under the urging of said spring means, said latch meansbeing disengaged from the second member upon relative rotation betweenthe first member and the inertia member, and means operated by slidingmovement of said second member for tripping the safety brake on theelevator car.

6. The brake tripping means of claim 5 in which the latch means isfixedly mounted on the inertia member and has a finger extending throughaligned openings in the first and second members, a latch lug on saidfinger bears on the face of the second member remote from the firstmember, and in which rotation of the inertia member relative to thefirst member causes said latch lug to move into a release recess in thesecond member.

References Cited UNITED STATES PATENTS 2,244,893 6/1941 Panter 188--1882,511,697 6/1950 Clift 187-90 FOREIGN PATENTS 335,056 4/ 1921 Germany.

EVON C. BLUNK, Primary Examiner.

H. C. HORNSBY, Assistant Examiner.

1. IN A SAFETY BRAKE SYSTEM FOR ELEVATOR, CARS BRAKE TRIPPING MEANSCOMPRISING, IN COMBINATION: A FRAME; A SHAFT JOURNALLED ON SAID FRAME;MEANS FOR ROTATING SAID SHAFT AT A SPEED WHICH IS DIRECTLY PROPORTIONALTO THE SPEED OF DESCENT OF THE ELEVATOR CAR; A ACCELEROMETER MEANS ONSAID SHAFT FOR DETECTING A RATE OF ACCELERATION OF SAID SHAFT IN EXCESSOF A PREDETERMINED MAXIMUM RATE, SAID ASCCELEROMETER MEANS HAVING APLURALITY OF RELATIVELY MOVABLE MEMBERS WHICH MOVE RELATIVE TO ONEANOTHER ONLY WHEN SAID MAXIMUM RATE OF ACCELERATION IS EXCEEDED; ANDMEANS CARRIED ON THE SHAFT AND MOVABLE RELATIVE TO THE SHAFT, SAID